Introduction to Forest Ecology & Measurement

Introduction to Forest Ecology & Measurement

Ellen Powell

Virginia Dept. of Forestry

Virginia Department of Forestry

⚫ Mission: We protect and develop healthy, sustainable forest resources for Virginians.

⚫ Vision: We envision forest resources that support and enhance a healthy living environment.

Forest Values

⚫ Wildlife habitat

⚫ Water quality

⚫ Renewable products (fuel, fiber, food)

⚫ Oxygen generation and pollutant removal

⚫ Carbon sequestration and storage

⚫ Recreational spaces

⚫ Natural cooling and energy savings

⚫ Pollinator sources

⚫ Soil building and erosion prevention

Succession

⚫ Succession is a pattern of change in plant communities over time.

⚫ Basic forest succession model:

– Grasses & Forbs --> Pioneer Tree Species --> Seral Species --> Climax Species

⚫ Disturbance sets succession back to an earlier stage.

SUCCESSION

⚫ Inevitable, continuous, determined by disturbance, a cycle, stages of: (grass, weeds, shrubs, trees)

⚫ A fundamental concept in ecology; refers to more-or-less predictable and orderly changes in the composition or structure of an ecological community. Succession may be initiated either by formation of new, unoccupied habitat or by some form of disturbance (e.g. fire, severe windthrow, logging) of an existing community.

Many Factors Influence a Forest

Hard to Control:

⚫ Soils

⚫ Nutrients

⚫ Moisture

⚫ Air (pollution)

⚫ Aspect

Easier to Control (in theory):

⚫ Sunlight availability

⚫ Species selection

⚫ Genetics

⚫ Competition

⚫ Pests (some)

Growing Conditions: Soil

⚫ Moist Soils: Red Maple, Sycamore, Green Ash, Hackberry, Sweetgum, Willow Oak, Loblolly Pine

⚫ Intermediate Soils: Yellow-Poplar, White Oak, Northern Red Oak, White Ash, Shortleaf Pine

⚫ Drier Soils: Scarlet Oak, Black Oak, Eastern White Pine, Chestnut Oak, Mockernut and Pignut Hickories

⚫ Note: Some species occur across a wide range of soils (e.g., southern red oak).

Topographic Factors

Slope – Degree of steepness

Erosion, soil depth

Aspect – Direction slope faces

SW, warmer and drier (white

oak)

NE, cooler and wetter

(hemlock)

Position – Upper/lower

Soil depth, nutrients

Growing Conditions: Light

⚫ Shade Intolerant: Loblolly and Shortleaf Pines, Northern Red Oak, Scarlet Oak, Yellow-Poplar, Sweetgum, Black Cherry

⚫ Moderately Shade Tolerant: White Oak, Southern Red Oak, Hickories, Ashes

⚫ Shade Tolerant: Red Maple, Persimmon, American Beech, Slippery Elm, Eastern Hemlock, Flowering Dogwood

Forest Stratification

⚫ Emergent (dominant) trees have crowns above the canopy.

⚫ The canopy level is the “forest roof”, with crowns of co-dominant and intermediate trees

⚫ The forest understory consists of young, suppressed or small species of trees and shrubs

⚫ The forest floor hosts seedlings; leaf litter; downed logs and other decaying material, and herbaceous plants.

Forest Structure

Upper Canopy

Dominant/Codominant

Lower Canopy

Intermediate

Understory

Suppressed

Forest Floor

Herbaceous cover

Forest Management

⚫ Dictionary definition: practical application of scientific, economic, and social principles to the maintenance of a forest to meet specific goals

⚫ Practical definition: growing trees, in a sustainable way, formany possiblereasons

Management goals are chosen

by the landowner!

Silviculture and Harvesting

⚫ Silviculture = growing trees

⚫ Silvicultural prescriptions often include harvest of trees.

⚫ Harvesting strategies mimic natural processes.

– Fires, floods, storms, insect and disease outbreaks, aging

Even-Aged Management

⚫ Regenerates trees with no or low shade tolerance (e.g. pines)

⚫ Over long term, can regenerate more shade tolerants from understory (e.g. oaks under pine)

– Clear Cut

– Seed Tree Cut

– Shelterwood Cut

Clear Cut

⚫ Removes all trees from stand at once, resetting the successional clock.

⚫ Economically efficient.

⚫ Provides full sunlight to shade intolerant species.

⚫ Creates flush of vegetation that may benefit some wildlife (food, cover).

⚫ May not be aesthetically pleasing for a few years

⚫ Regeneration methods:

– Stump or root sprouts (hardwoods)

– Seed (pine or hardwoods)

– Planting (usually pine)

Clearcut – Even Aged

⚫ All trees within the harvest area are cut and removed

⚫ Favors shade-intolerant species

⚫ Produces sawtimber, pulpwood, chip n saw

⚫ Early successional habitat

Clear Cutting vs. Land Clearing

⚫ Clear cutting is NOT the same as land clearing!

⚫ A clear cut is a harvest method that sets the stage for a new forest.

⚫ Land clearing may initially look similar, but it leads to a change in land use (e.g., development).

Seed Tree Harvest

⚫ Leaves scattered high-quality trees to disperse seed.

⚫ Number left per acre depends on species, crown size, dispersal traits and management goals.

⚫ Effective for shade-intolerant species.

⚫ Improves control of seed origin (in theory).

⚫ Sacrifices some harvest volume.

Seed-Tree Cut – Even Aged

⚫ Favors light-seeded species

– Pine and Poplar

⚫ Identify 6-8 good seed bearing trees per acre

⚫ Remove the rest of the trees

⚫ Seed-trees provide additional habitat

Seed Tree Harvest

Shelterwood Harvest

⚫ Retains enough trees in initial cut for some percentage of crown closure (often 50-60%)

⚫ Effective for many shade tolerances, depending on amount of crown closure

⚫ Good control of seed origin (in theory)

⚫ Retains some mast production for wildlife

⚫ Management intensive

– Multi-phase harvest requires more entries to stand.

– Sacrifice of initial timber volume

Shelterwood Cut – Even Aged

⚫ Favors heavy seeded species

– Oak

⚫ Leave 10 -12 seed producing trees per acre

⚫ Remove the rest of the trees

⚫ Overstory trees help establish reproduction of the stand

⚫ Overstory trees may be removed later

Shelterwood Harvest

Uneven-Aged Management

Regenerates species

with moderate to

high shade

tolerance ⚫ Selection Harvest

⚫ Group Selection

Harvest

Selection (Single Tree) Harvest

⚫ Works for shade-tolerant species only.

⚫ Retains genetically superior, healthiest trees in all size/age classes.

⚫ Aesthetically pleasing (minimal visual disturbance).

⚫ Time consuming to establish a timber sale.

⚫ Damage to soil, water and remaining trees is a concern with multiple stand entries.

⚫ NOT to be confused with diameter-limit cutting or “high-grading.”

Single Tree Selection – Uneven Aged

⚫ Favors shade-tolerant trees

– Beech, Sugar Maple, Hickory

⚫ Constantly removing individual trees over time

⚫ Multiple entries into the stand

⚫ Road layout and proper felling techniques are crucial

⚫ Rarely practiced

Please, No High-Grading!

⚫ Common practice through mid-20th century and reason for existence of many low quality hardwood stands today

⚫ Removes the best sawtimber, leaving small, deformed, or less healthy trees to grow

⚫ Destructive to future forest health and productivity

⚫ Unfortunately, still occurs more than it should in Virginia!

Diameter Limit Cutting – Uneven Aged

⚫ Trees above a certain diameter are cut and nothing else

⚫ Considered a “High Grade”

– Taking the Best and Leaving the Rest

⚫ Does not favor any species

⚫ Not a recommended practice

Group Selection Harvest

⚫ Removes small (1/4- to 2-acre) blocks of trees.

⚫ Removes smaller-diameter, poor-formed, unhealthy and undesirable trees.

⚫ Stimulates growth of the remaining trees by reducing competition.

⚫ Creates gaps in the forest canopy, which can benefit some wildlife species.

⚫ Requires care in harvest planning to prevent damage to site.

Group Selection – Uneven Aged

⚫ Create small “patch clearcuts” throughout the stand

⚫ Creates a mosaic of age classes across the stand

⚫ Favors intermediate shade-tolerant species

– Northern Red Oak

⚫ Benefits many wildlife species

Group Selection Harvest

Salvage Cut

⚫ Usually performed in stands that have been somehow damaged

– Fire

– Ice

– Insects and Disease

– Natural Disasters

⚫ Some revenue generated

⚫ Make way for new forest

Site Preparation

⚫ Prepares site for establishment of new trees

⚫ Common methods include…

– Fire

– Chemical applications

– Mechanical methods (e.g., drum chopping, shearing and bedding,windrowing)

Intermediate Prescriptions

⚫ Pre-commercial thinning frees the healthiest trees to grow.

⚫ Timber stand improvements

⚫ Crop tree release (hardwoods)

⚫ Commercial thinning (also generates income)

⚫ Prescribed burning reduces fuel load, controls competition, stimulates herbaceous growth.

⚫ Herbicide treatments control competition and/or invasives.

⚫ Fertilization (not common in Virginia)

Pre-Commercial Thinning

⚫ Usually performed in Pine stands

⚫ Used to improve spacing of a younger stand

⚫ Improves health of the stand in the future

⚫ No income generated

Commercial Thinning

⚫ Performed in Pine and Hardwood stands

⚫ Improves spacing

⚫ Improves health and vigor of the stand

⚫ Produces income

⚫ Releases desirable species

Crop Tree Release - CTR

⚫ Usually performed in hardwood stands

⚫ Releases desirable trees from competition

⚫ “Crop trees” are identified and trees touching it are cut

⚫ No income generated

Timber Stand Improvement - TSI

⚫ Usually performed in Hardwood stands

⚫ Removes less desirable species from the stand

⚫ Produces some income

⚫ Improves stand conditions for desirable trees

Forestry and Water Quality

⚫ Problems from forestry can occur during harvests (mainly from roads and stream crossings).

⚫ Forestry Best Management Practices (BMPs) minimize erosion and sedimentation from forestry operations.

⚫ BMPs are voluntary in Virginia, but water quality laws are enforceable.

Forest Management Issues

⚫ #1 - Loss of forest land base / urbanization

– Fragmentation

– Parcelization

⚫ History of poor management

– High-grading

– Fire suppression

⚫ Competition from invasive species

⚫ Disease and insect threats